1. Field of the Invention
The invention set forth in this specification pertains to new and improved sign structures. More specifically, it pertains to sign structures that are especially desirable because of the fact that they can be easily and conveniently manufactured at a comparatively nominal cost.
2. Description of Related Art
The most closely related prior art sign structures commonly include a centrally located panel adapted to carry one or more indicia. The panel is usually surrounded and held by a peripheral frame. Normally such closely related sign structures are of such size as to be capable of being used in windows, building lobbies or the like. Desired indicia can be formed into or located on the panel, or the panel can hold a surface covering which, in turn, is adapted to carry one or more items to be displayed. It is frequently desired to form the panel so that it is provided with parallel grooves or channels which are adapted to support and display indicia such as letters.
The panels have been commonly formed out of sheets of a "solid" material such as plywood or particle board. The grooves are provided by first sawing parallel grooves in the solid panel and then pressing a flexible sheet of felt or the like into the grooves. In such structures, the felt or the like is used to provide a frictional connection between the sides of the grooves and extensions provided on the back of the indicia. The felt is usually adequate to prevent the indicia from moving during limited handling of a sign structure, yet allows the indicia to be replaced whenever desired. Such panels have also been formed by molding essentially solid structures out of synthetic rubber type polymer compositions.
The frames commonly used with panels are normally constructed in what can be regarded as a "traditional" manner where the frames and panels are assembled into an essentially "unitary" structure. Recently, both the frames and the panels have been constructed of comparatively thin sheets of a thermoplastic polymer material. However, both the solid-type and the sheet-type of sign construction have significant commercial drawbacks and limitations.
The signs tend to be relatively expensive to manufacture and comparatively heavy when "traditional" frames are used with either "solid" panels or sheet panels, as discussed in the preceding. Such signs are, therefore, comparatively expensive to ship. On the other hand, when sign structures are entirely formed of thin sheets of a thermoplastic material, the costs of manufacturing such sign structures tend to be significantly reduced. Also, because of the relative light weight of such sign structures, they tend to be comparatively inexpensive to ship.
However, the advantages associated with sheet-type construction are achieved at a price. It is considered that these sign structures tend to be less attractive and rigid than sign structures employing "traditional" frames and "solid" panels. In particular, the walls of such sign structures are frequently so thin that they are pierced when the rear extension of replaceable indicia are inserted in the parallel grooves. In addition, it is considered that there is a degree of danger that sign structures formed from such thin sheets may tend to warp after they are constructed, particularly when they are used in a window in a hot area where the temperature of the sign conceivably could reach the softening point of the polymer material in the sign.
The detrimental factors referred to in the preceding paragraph are easily illustrated by referring to a current commercial type of "shutter" sign manufactured from a sheet of thermoplastic material. Such sign structures are typically formed from a single sheet of thermoplastic polymer material using conventional vacuum forming techniques. They usually include a peripheral frame that is integral with first and second panels that are offset from one another and separated by a slot. Such signs typically include extruded tracks that extend along the slot between the first and second panels. A shutter is usually held by the tracks so as to be capable of being moved between a position covering the front surface of the first panel to a position exposing this front surface.
A grooved sheet capable of holding indicia is normally secured to the front surface of the first panel in such "shutter" signs. It is considered obvious that such a sheet could also be adhered to the front surface of the second panel or omitted. When no such grooved sheet is used on either of these front surfaces, such surfaces can either be formed so as to contain permanent indicia or formed flat so as to be capable of supporting a paper or the like containing the desired indicia.
Sign structures as indicated in the preceding paragraphs are utilitarian and are desirable for several reasons. One is that they weigh comparatively little and, hence, can be shipped cheaply. Another is that they are comparatively easy and inexpensive to manufacture because of the inherent character of vacuum forming.
However, it is considered that normally they do not have the desired "substantial" type appearance desired for many commercial applications because of the thin character of the sheets used in manufacturing them. In particular, because of factors related to vacuum forming, they are frequently so thin that there is a significant danger of the rear extensions of indicia puncturing them. Moreover, it is considered that they are excessively prone to warping because of the character of the thermoplastic sheets used in their construction.